More than a half a million tweets, more than that, in fact, this afternoon about the actor. Tonight here, some of his most famous roles and how becoming a father changed him. There were so many indelible performances. Here, from "The master." You've wondered from the proper path, haven't you? Reporter: Philip Seymour Hoffman winning the Oscar for best actor for his role in the 2005 film "Capote," his portrayal of the famous writer. Told me I had a phone call. And it was my step-father, Joe capote calling to say that my mother had died. I flew home to New York, terribly distraught. But when I got to the apartment, I could see that Joe was even worse shape than I was. He grabbed my hand and he said to me, talk. Reporter: Hoffman grew up outside Rochester, New York. Telg "The New York times" that at 12 he saw a local production of "All my sons," his first glimpse of the acting world up close. When he won that Oscar, an emotional and grateful actor thanking the mother that took him to that play. We're at the party, ma, you know? And she took me to my first play and she stayed up with me and watched the ncaa final four and my passions, her passions became my passions, and you know, be proud, mom, because I'm proud of you and we're here tonight and -- it's so good. Thank you. Reporter: He was in more than 40 films. There was "Doubt," opposite Meryl Streep. He played father Flynn. You've had a fundamental mistrust of me before this incident it was you that warned sister James to be on the lookout, wasn't it? That's true. So, you admit it! Certainly. Why? I know people. That's not good enough. Reporter: Hoffman would never say whether he thought the priest he portrayed was innocent or guilty. So many fans this Sunday, remembering their own favorite roles. The boarding school bully in "Scent of a woman." Scotty J. In "Boogie nights." Here, here, here. Keep coming. All right, open them. This is it. Cool! Yeah! You want to get inside? Reporter: In "The savages," two grown children, caring for an ailing parent. We still need somebody to take care of him. We can't afford that. You heard the nurse. Dad falls? He's disoriented. He hasn't fallen once since we've been here. Don't make me to be out the evil brother. We're doing this together, right? Reporter: He was a star on stage, too. His arresting performance in "Death of a salesman" on Broadway. Often seen in his New York City neighborhood. When he wasn't acting, he was with his children. He told ABC news he became a different man after having them. When you have children, the idea of heartbreak changes. The whole definition of what heartbreak means takes on a whole different meaning. Reporter: And about himself, that boy who saw his first play at 12, he told "The times" the experience was like a more can to me, but for me, acting is torturous and it is torturous because you know it's a beautiful thing. The loss of Philip Seymour Hoffman tonight. So many people thinking about his three children and his long-time partner, we mentioned earlier. Much more on the actor tomorrow morning on "Good morning America."

This transcript has been automatically generated and may not be 100% accurate.

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